Problems encountered in the process of CTP equipment and solutions

In 2014, the author's Shaoxing Daily Newspaper Printing Co., Ltd. officially purchased a Kray UV- CTP device and a Kodak Quansheng 800CTP device, completely eliminating the photo-setting equipment and officially opening the application path of CTP. Here, the author has sorted out some problems and solutions encountered in the process of using CTP equipment, and shared with the readers.

"Pit" for equipment maintenance

1. Plate machine drive gear wear

Once the equipment was in normal use, a burning smell suddenly appeared. After inspection, it was found that the butter and oil of the transmission gear of the plate printing machine were exhausted, and the gear of the entire plate printing machine was severely worn due to the lack of timely filling, resulting in a scorching odor.

In response to this problem, our company has made special provisions to require operators to open the cover of the plate processor every six months, adding butter and oil to prevent the transmission gear from wearing.

2. Double version

The problem of double sheeting often occurs during the initial stages of using UV-CTP equipment. After careful observation, there is a double sensor between the device's plate feeder and the CTP mainframe. When the laser is exposed to the plate, some dust will be generated. After a period of time, the dust accumulation will reduce the sensitivity of the double sensor. At this time, if two plates are simultaneously mounted on the head clip of the CTP main body, the double sensor cannot sense the signal in time, which may easily cause the printing plate to be unable to be clamped, and is extremely easy to cause the device when the device is running at a high speed. damage.

In response to this problem, the company requires the plate-making personnel to carefully carry out the maintenance work of the equipment, and regularly wipe the equipment. For the location that cannot be wiped, the air gun must be used to remove dust. Since then, the double-page issue of the device has never appeared.

3. The production environment is not suitable

The CTP equipment has high requirements on the ambient temperature and humidity. In the winter and summer, it is necessary to open the air conditioner to keep the working temperature of the workshop constant. In the past work, it was encountered that the CTP equipment could not be properly prepared due to the low ambient temperature.

In addition, CTP equipment has high requirements for gas sources. Dry, clean air can improve equipment performance and extend equipment life. When conditions permit, it is best to use it exclusively. Our company is located in the south of the Yangtze River, and the air humidity is high. Therefore, the company requires the plate-making personnel to eliminate the moisture in the air compressor and the condenser every week to meet the requirements of the CTP equipment for the gas source.

At present, our company attaches great importance to the maintenance and repair of CTP equipment, not only attaches great importance to the daily maintenance of equipment, but also invites professional engineers to maintain the laser head and screw shaft of the equipment every six months.

"through" linearization curve

In order to ensure the quality of the printing plate, our company specially purchased a printing plate measuring instrument and made measuring rods on the printing parts of the printing plate. Immediately after the first plate is produced, the dot values ​​of 3%, 50%, and 100% color patches are measured. Since the linearization curve has been set, the plate-making conditions of the device are constantly changing. To judge whether the obtained printing plate is satisfactory, it is necessary to measure the color block data. For our company, when the actual measured values ​​of 3%, 50%, and 100% color blocks are around 1.5%, 45.0%, and 97.0%, the dot reduction and printing durability of the printing plate are in an optimal state.

Get two major plate making problems

Grinding

The traditional PS version is fully exposed by iodine gallium lamps, and the printing durability is relatively high, reaching more than 100,000 copies. The maximum number of newspapers printed by our company is 70,000. When CTP is first used, when it is printed to about 50,000, there will be different degrees of grinding.

After many attempts, we finally solved this problem by: firstly, reducing the printing pressure by adjusting the roller pressure and the thickness of the lining, thereby increasing the printing durability of the printing plate; then, after the printing machine is adjusted to the optimum state, Adjust the platemaking related parameters to improve the quality of the plate. Through continuous exploration, we finally stabilized the printing resistance of CTP plates at 70,000 copies.

2. The plate is dirty

There are many reasons for causing the plate to get dirty, such as weak laser, low developer concentration, and low temperature setting. It has been found through practice that the most effective way to detect the dirtyness of the printing plate is to drop a drop of anhydrous acetone in the blank part of the printing plate. When the anhydrous acetone is volatilized, check whether the droplets have traces on the surface of the printing plate. If there is, it may happen to be dirty when printing. For the dirty printing plate, you can enhance the laser intensity, increase the concentration of the developer, and extend the printing time. If necessary, you can solve the problem by quickly walking the plate in the plate processor. Today, anhydrous acetone is strictly controlled by the public security department. It can be replaced with anhydrous alcohol, but the detection effect is much worse.

Non-small rehydration

Due to the small amount of single-day printing, the cycle of changing the developer is generally half a month. However, in the initial stage of using the CTP device, the developer was used for less than a week, and the punched plate was dirty. By measuring the conductivity of the developer of the plate processor, it was found that the conductivity of the new developer was about 75 μs, and after only one week, it was only about 65 μs, and the conductivity decreased, that is, the concentration of the developer decreased. After analysis: the developer is actually a strong alkali. After a period of use, the alkalinity decreases, and the replenishing liquid delivered is the same as the concentration of the developer. Therefore, after the developer is replenished, the alkalinity cannot be restored to the normal level, which will result in The plate is dirty.

In response to this problem, we asked the plate supplier about the ratio of developer to replenisher. As a result of our analysis, they did not notice the problem of the ratio of developer to replenisher. The developer and replenisher provided. Both were 1:4. Later, our company asked the supplier to increase the concentration of the replenishing solution to 1:3. As a result, the life of the developer was greatly extended.

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